Outer Limits episodes are available on video and on DVD from Amazon.com
Robert Culp plays a man who, by virtue of a metal plate in his skull, overhears two alien "rocks" plotting the overthrow of the Earth by invading peoples' minds. The two strange rocks in Dr. Temple's geology lab are actually protoplasmic alien invaders capable of entering and controlling a human "Corpus." ... And the message is "kill." Later, when Temple is alone, the rocks assume the forms of black, living, pulsating creatures that slither across the cabinet and forcefully enter Templešs body as he struggles for his life. They are creatures from another planet who wish to take over Earth by using human bodies as their hosts.
"Corpus Earthling" (1963)
First, the aliens take over the geologist (Barry Atwater of Star Trek episode #77) to try and find the other geologist. Eventually, his own wife (Temple's assistant) is invaded, and the whole episode is a beautiful creeping terror.
Writer: Orin Borstein
Director: Gerd Oswald
Salome Jens, David Garner, Ken Renard